Wavelength division multiplexing (WDM) system has attracted more and more interest in the past several years for building ultra-high aggregated data rate optical network and optical interconnects, given that interconnection has been considered as the bottleneck for the next-generation computing systems. Microring resonators are one of the most popular devices to form the important building blocks of on-chip network and optical interconnects, owing to their small footprint, small capacitance and low power consumption. Much progress has been made in the past decade in designing and demonstrating microring-based modulators, filters, switches, lasers, and other structures.
The commonly used ring-based WDM transmitter architecture is shown in FIG. 1, in which a series of ring modulators share one bus waveguide. This architecture is referred to as “common-bus” architecture. This configuration does not require each ring modulator to be associated with a specific wavelength in the WDM system. Instead it offers the flexibility of assigning rings to the closest wavelength so as to minimize the overall tuning power. However, a comb laser or pre-multiplexed laser sources are required at the common input and cross-modulation may be introduced since the light in the bus waveguide passes through multiple ring resonator modulators.
Automated thermal stabilization is particularly challenging in the common-bus design, due to the fact that multiple wavelengths are always present at the bus waveguide and interact with each ring modulator but the monitoring photo detector is naturally insensitive to wavelength.
There is a need for an improved apparatus for multiplexing a plurality of wavelengths onto a common optical fiber.